The EPON is a new generation broadband passive optical integrated access technology based on the Institute of Electrical and Electronics Engineers (IEEE) 802.3-2005 Section 5 Standard. As shown in FIG. 1, the system usually consists of an OLT, an Optical Distribution Network (ODN) and an Optical Network Unit (ONU)/Optical Network Termination (ONT). The OLT provides a network side interface for the EPON system, and the ONU provides a user side interface for the EPON system. The ODN consists of single mode fibers and passive optical devices such as an optical splitter and an optical connector, and provides optical transmission medium for a physical connection between the OLT and the ONU. The ODN is usually of a point-to-multipoint structure, that is, one OLT can be connected with a plurality of ONUs via the ODN. If an ONU directly provides a user port function, for example, an Ethernet user port for Internet use of a personal computer (PC), it is called an ONT.
In one ODN, the optical fiber distances from the ONUs or the ONTs to the OLT are different. Due to the attenuation of the optical fiber transmission line, near ONUs or ONTs can work normally with a relatively low optical power, while far ONUs or ONTs need a relatively high optical power to work normally. In the existing EPON system, in order to make the OLT stably receive data from all ONUs or ONTs, the optical powers of the optical modules of the ONUs or the ONTs are fixedly configured according to the farthest distance supported by the OLT. In this way, for near ONUs or ONTs, the transmission power which meets the requirement of stably receiving data by the OLT is far less than the transmission power fixedly configured according to the farthest distance supported by the OLT, therefore the waste of the optical power is caused.